Nature of the Atmosphere (part 2)

Question 1

What does dew point mean? (AC00-6)

Answer 1

1. Dew point is the temperature to which a sample of air must be cooled to attain the state of saturation

Question 2

When temperature and dew point are close together (within 5°), what type of weather is likely? (AC00-6)

Answer 2

1. Visible moisture in the form of clouds, dew, or fog
2. These are ideal conditions for carburetor icing

Question 3

What factor primarily determines the type and vertical extent of clouds? (AC00-6)

Answer 3

1. The stability of the atmosphere

Question 4

Explain the difference between a stable atmosphere and an unstable atmosphere. Why is the stability of the atmosphere important? (FAA-H-8083-25, AC 00-6)

Answer 4

1. A stable atmosphere makes vertical movement difficult
2. In an unstable atmosphere, vertical air movements can lead to extensive vertical cloud development, turbulence, and severe weather

Question 5

List the effects of stable and unstable air on clouds, turbulence, precipitation and visibility. (AC00-6)

Answer 5

1. Stable: Stratiform clouds, light turbulence, steady precipitation, and fair to poor visibility
2. Unstable: Cumuliform clouds, rough turbulence, showery precipitation, and good visibility

Question 6

When significant precipitation is occurring at the surface, how thick can you expect the clouds to be? (AC00-6)

Answer 6

1. Significant precipitation usually requires clouds to be at least 4,000 feet thick
2. The heavier the precipitation, the thicker the clouds are likely to be

Question 7

During your preflight planning, what type of meteorological information should you be aware of with respect to icing? (AC 00-6)

Answer 7

1. Location of fronts
2. Cloud layers (reference PIREPs and area forecasts)
3. Freezing level(s) (reference PIREPs and area forecasts)
4. Air temperature and pressure (Icing tends to be found in low-pressure areas and at temperatures at or around freezing)

Question 8

What is the definition of the term freezing level and how can you determine where that level is? (AC 00-45)

Answer 8

1. The freezing level is the lowest altitude in the atmosphere at which the air temperature reaches 0°C
2. It is possible to have multiple freezing layers when a temperature inversion occurs above the defined freezing level
3. Sources of icing information are: PIREPs, AIRMETs, SIGMETs, and winds and temperatures aloft (for air temperature at altitude)

Question 9

What conditions are necessary for structural icing to occur? (AC00-6)

Answer 9

1. Visible moisture
2. Below freezing temperatures at the point moisture strikes the aircraft

Question 10

What are the two main categories of aircraft icing? (AC 00-6)

Answer 10

1. Structural icing: referring to ice that forms on aircraft surfaces and components
2. Induction icing: referring to ice that forms in the engine’s induction system

Question 11

Name the three types of structural icing that may occur in flight. (AC 00-6)

Answer 11

1. Clear ice: forms when a liquid drop flows out over the aircraft surface, freezing as a smooth sheet of ice
2. Rime ice: forms when drops are small, the liquid drop freezes rapidly before it has time to spread out over aircraft surface
3. Mixed ice: forms when drops vary in size or when liquid drops are intermingled with snow and/or ice particles. The ice particles become imbedded in clear ice, building a very rough accumulation

Question 12

What action is recommended if you inadvertently encounter icing conditions? (FAA-H-8083-15)

Answer 12

1. The first course of action should be to leave the area of visible moisture
2. Descend to an altitude below the cloud bases
3. Climb to an altitude above the cloud tops
4. Turn to a different course